Gas reaction rotors



May 3, 1960 J. E. M DONALD GAS REACTION ROTORS 3 Sheets-Sheet 1 Filed Dec. 10, 1956 J'ohn E. Mcaonald y 1960 J. E- MCDONALD 2,935,245

GAS REACTION ROTORS Filed Dec. 10, 1956 3 Sheets-Sheet 2 INVENTOR 5) We 7, K ?a ;1

ATTORNEY May 3, 1960 J. E. MCDONALD CAs REACTION ROTORS 3 Sheets-Sheet 3 Filed Dec. 10, 1956 15204222202 Joizii/ E. MaDonaZd, a W W vrlfoz ney than! a iinited States batent Q? GAS REACTION ROTORS John E. McDonald, Newton, Mass, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa, a corporation of Pennsylvania Application December 10, 1956, Serial No. 627,459

9 Claims. (Cl. 230-114) This invention relates to gas reaction rotors having airfoil blades, and has as an object to improve the performances of such rotors.

This application is a continuation-in-part of my copen'ding applications, Serial No. 401,542, filed December 31, 1953, now abandoned, and Serial No. 479,561, filed January 3, 1955, now abandoned.

A particular size of fan rotor rotated at its design speed will provide an increase in gas pressure. Heretofore, for providing a larger increase in gas pressure from a rotor of the same type, the rotor had to be provided with more blades or had to be made a larger diameter. Rotating such a rotor at higher than design speed in an attempt to provide an increase in gas pressure does not provide satisfactory performance.

I have found that a fan rotor having airfoil blades can be made to provide a much larger increase in gas pressure than is normal by providing the driving sides of the blades with slots adjacent their trailing edges, and by forcing gas outwardly through such slots at substantial angles to the chord lines of the blades. important commercial advantages. It enables a smaller, less costly rotor to provide the same increase in gas pressure that a larger, more costly rotor has heretofore been used for. It enables a rotor designed for normal loads to easily handle peak loads. It also provides an eflicient volume control, since the flow of gas out of the slots can be varied for varying the gas pressure increase. Less power is required.

Another object of this invention is to increase the gas pressure provided by a fan rotor.

Another object of this invention is to provide an eflicient volume control for a fan.

This invention will now be described with reference to the annexed drawings, of which:

Fig. 1 is a side section of an airfoil blade embodying this invention;

Fig. 2 is a plan view of the blade of Fig. 1, and shows also, a portion of the side and center plates of the rotor of a centrifugal fan;

Fig. 3 is a side section on a reduced scale, with a portion of its side plate removed, of a centrifugal fan rotor embodying this invention;

Fig. 4 is an end elevation of the rotor of a double inlet centrifugal fan embodying this invention, having a hollow shaft connected to a source of compressed air which supplies the compressed air and the center plate of the rotor into its hollow airfoil blades;

Fig. 5 is a side elevation, partially in section, of a single inlet rotor embodying this invention, with an auxiliary fan attached to its back plate and supplying air under pressure through the back plate into the hollow airfoil blades;

Fig. 6 is an enlarged side section of another form of airfoil blade embodying this invention,

Fig. 7 is an enlarged, fragmentary side view with a portion of the side plate removed, of another centrifugal This has several 2,935,245 ?atented May 3, 1960 fan rotor embodying this invention, including blades like that of Fig. 6; and

Fig. 8 is a view similar to Fig. 7 except that it has blades of a different form.

Fig. 3 shows a rotor 16 which is adapted to be rotated in a counter-clockwise direction, and has what are known as backwardly curved airfoil blades 11 supported between its side plate 12 and its center plate 13. The convex sides of the blades 11 are their driving sides, and the opposite sides are their trailing sides. The rotor has a shaft 14 which has a central passage 15 connected through a seal and a valve 16 to a source 17 of compressed air. The valve 16 has a control lever 13 which has at its upper end an indicator 19 facing a calibrated scale 20.

The passage 15 in the shaft 14 connects through a larger axial passage in the center plate 13 with radial passages 21 in the center plate, and the passages 21 connect through passages 22 with the interiors of the blades 11. The blades 11 have slots 24 in their driving sides adjacent their trailing edges. The compressed air passing out the slots 24 causes the rotor It) to provide a much larger increase in gas pressure than it otherwise would.

The valve 16 can be adjusted to control the volume of air supplied into the fan blades, and the degree of gas pressure increase. With the valve closed, the rotor operates in a conventional manner. The scale 20 can be calibrated to show gas pressure or volume.

Fig. 5 shows a rotor 33 for a single inlet fan. It has a side plate 31 and a back plate 32 between which are sup ported hollow airfoil blades 11 having slots 24. The back plate 32 has secured thereto on its side opposite to the blades 1.1, an auxiliary fan rotor consisting of radially extending plate-type blades 33 and a side plate 34. The outer ends of the blades 33 terminate inwardly of the passages 22A which connect with the interiors of the blades 11 so that the gas discharged from the blades 33 passes into the interiors of the oiades fli out their slots 24. The side plate 34 has a central opening 35 around the shaft 36 of the rotor 3t forming an air inlet passage into the auxiliary fan rotor. A cylinder 38 is slidable on the shaft 36 and within a ring 39 on a back sheet 40, and can be moved towards and away from the inlet passage opening 35 for opening or dampering the passage 35. The cylinder 38 thus serves as a pressure control for the auxiliary and main fans.

Fig. 6 illustrates another form of airfoil blade 11A that can be used, and which has a slot 24A in its driving side adjacent its trailing edge which discharges gas at an angle of about to the chord line of the blade. It has been found that for maximum performance, this angle identifled on Fig. 6 as 0, should be between 15 and The slot widths preferably should range between 0.5% and 10% of the chord length.

Fig. 7 illustrates a rotor 10A having two additional forms of airfoil blades that can be used. Blade 11B has a slot 40 at the center of its nose through which gas impacted by the ram action of the blade nose enters into the interior of the blade, an passes out the slot 24A to provide an increase in the pressure of the gas handled by the rotor.

Blade 11C of Fig. 8 has a slot 41 formed by an upturned lip 42 of the driving side of the blade a short distance behind its nose. The lip 42 acts as a scoop directing air or other gas impacted by the blade into its interior. The blade 11C has a slightly modified outlet slot 24B formed at the trailing edge of the blade between the trailing end of the driving side of the blade, and the outwardly turned trailing end of the trailing side of the blade.

In a fan rotor having a diameter of 30" with eight equally spaced airfoil blades similar to that of Fig. 6,

- E with chord, rotated at a speed of 1200 rpm. compressed air supplied into the blades in an arrangement similar to that of Figs. 3 and 4, provided an output pressure 40% greater than wasobtained from the same rotor Without supplying compressed air into its blades. The pressure of the air leaving the-slots was 24? of water, about four. times fan output pressure. Large output pressure increases above normal are obtained at lower slot pressures. The improvement starts at a slight slot pressure above zero pressure, and the greatest rate of improvement is in the range just above zero slot pressure.

The compressed gas passing out the slots definitely does not act to maintain boundary, layer flow, On the contrary it greatly'disturbs boundary layer flow adjacent the trailing edges of the blades. The action istnot, exactly understood. Air foil fan blades do not act like, airplane wings sincethey. are rotated instead of advancing alongrelatively straight paths. Many more variables are involved thanin the case of airplane wings, such as centrifugal force, Coriolis forces, and theefiect of the casing around the rotor. It is believed, however, that the air or other gas discharged from the blade slots acts somewhat as an outwardly extending flap at the trailing edges of the blades, but without the disadvantages of physical flaps such as mass, resistance, and the mechanical problems of adjustment.

In the annexed claims, backwardly curved airfoil blades? are defined as airfoil blades having convex gas impacting sides, having leading edges or noses which impact the gas passing the blades, and having trailing edges which are downstream with respect to the gas flow, of the noses." I

The center plate of a double inlet fan is, of course, the back plate of each fan section, and corresponds to the back plate of a single inlet fan rotor. Therefore, the term back plate as used in the annexed claims should be interpreted as a center plate where the fan involved is a double inlet fan.

What is claimed is:

l. A centrifugal fan rotor having a front plate and a back plate, a plurality of backwardly curved, airfoil blades supported between said plates with their trailing edges spaced a greater distance from the axis of said rotor than their noses are spaced, said blades having convex ,gas compacting sides curving from their noses to their trailing edges away from the direction of rotation of said rotor, a radial line extending through the nose of each blade being spaced a substantial distance ,at the periphery of said rotor in a direction opposite to said direction of rotation of said rotor from a radial line extending through the trailing edge of the same blade, said blades having slots in their gas impacting sides adjacent their trailing edges, and means for supplying gas under pressure into said blades and out said slots, said slots being angled and positioned to direct the gas discharged therefrom forwardly at substantial angles to the chord lines of said blades whereby the gas discharged from said slots deflects the main gas stream passing said gas impacting sides of said blades outwardly from said trailing edges.

2. A centrifugal fan rotor as claimed in claim 1 in which said slots are positioned and angled to direct the gas discharged therefrom at angles between and 120 to said chord lines.

3. A centrifugal fan rotor as claimed in claim 2 in which the widths of said slots are between 0.5% and 10% of the lengths of said chord lines. 7

4.-A centrifugal fan rotor as claimed in claim 1 in which the widths ofsaid slots are between 0.5% and 10% of the lengths of said chord lines.

5. A centrifugal fan rotor as claimed in claim 1 in r '4 which the means for supplying gas into'said blades comprises a plurality of passages in said back plate connecting with the interiors of said blades, includes a source of compressed gas connected to said passages, and includes means for varying the volume of compressed gas supplied by said source to said blades.

6. A centrifugal fan rotor .as claimed in claim 5 in which the source of compressed gas comprises an auxiliar fan rotor on the opposite side of said back plate from said blades, said auxiliary rotor having blades which discharge into said passages.

7. A centrifugal fan motor as claimed in claim 1 in which the means for supplying gas-into said blades comprises openings in the noses of the blades through which the gas impacted by said noses is forced to enter by ram action.

8. A centrifugal fan rotor as claimed in claim 1 in hich t me ns o .supp y nss sin o said b ades cem- Prises op nin srin a d. g s imn ct gs des o said lad between said slots and said noses, and scoops at the downstream sides of the openings arranged to force gas impacted by said scoops into said openings.

9.- A rotor for a double inlet centrifugal fan comprising a shaft, a center plate and a pairv of side plates attached to said shaft, a plurality of backwardly curved, airfoil blades supported between said centerrplate and side plates, said blades having their trailing edges spaced a greater distance from said shaft than'their noses are spaced, said blades having convex gas compacting sides curving from theirnoses to' their trailing edges away from .the direction of rotation of said rotor, a radial line extending through the nose of each blade being spaced a substantial distance at the periphery of said rotor in a direction opposite to said direction of rotation of said rotor from a radial line extending through the trailing edge of the same blade, said blades having slotsin their gas impa ting sides adjacent their trailing edges, rneans including a source of compressed gas, a passage in said shaft connected to said source and passages in said center plate connected to said shaft passage for supplying compressed gas from said source into said blades and out said slots, and means for varying the volume of gas supplied by said source into said shaft passage, said slots being positioned and angled to' direct gas discharged therefrom forwardly at substantial angles to the chord lines of said blades whereby the gas discharged from said slots deflects the main gas stream passing said gas mpacting sides of said blades outwardly from said-trailing edges.

References Cited in the fileiof this patent QU IED. STAT P T T Re. 23,108 Stalker May 3, 1949 736,952 Fox Aug. 25, 1903 2,052,869 Coanda, Sept. 1, 1936 2,111,136 Bauer Mar. 15,1938 2,136,403 Vance et al Nov, 15, 1 938 2,305,226 Stalker Dec. 15,1942 2,344,835 Stalker 'Mar. 21, 1944 2,476,002 Stalker -r July 12, 1949 2,501,614 Price Mar. 21, 1950 2,597,510 McBride May 20, 1952 2,825,532 Kadosch et al Mar. 4, 1958 FOREIGN PATENTS 400,913 Great Britain 1933 475,711 Germany May 2, 1929 586,010 Germany July 9, 1931 608,703 Great Britain .Sept 20, 1948 838,209 France. Nov. 28, 11938 

